In conventional microcellular wireless communication systems, timing advance is not supported because portable units and local fixed access units are typically within 1000 feet of the radio port. One such microcellular wireless communication system is the personal access communication system (PACS) defined by the Joint Technical Committee as Air Interface Specification PN3418. In such conventional systems, timing advance is not necessary since the maximum delay can be compensated for by a timing adjustment algorithm defined by the air interface.
However, if the operating environment were extended to applications using a rural wireless fixed access unit or using a wired cable service, a fixed bulk delay is introduced into the system. Conventional microcellular systems will not operate in such applications.
One possible solution to this problem is provided in cellular communication systems where a subscriber's per call access technique provides information to determine whether to perform timing advance. Although this method could be applied to microcellular systems, modifying a subscriber's per call access technique would add undesirable cost and complexity to the system. Further, adding a process for performing timing advance on a per call access basis would degrade overall system performance and would interfere with subscribers that do not require timing advance.
Accordingly, there is a need for a method and apparatus for performing timing advance for rural wireless fixed access subscribers without interfering with other subscribers who do not require timing advance.